Polo-like kinases (PLKs) are serine/threonine kinases that play important roles in regulating processes in the cell cycle. There are four PLKs disclosed in the state of the art, i.e. PLK-1, PLK-2, PLK-3, and PLK-4. PLKs play a role in the entry into and the exit from mitosis in mammalian cells. Especially for PLK-1 a central role with respect to the regulation of mitosis was shown (Glover et al. 1998, Genes Dev. 12:3777-87; Qian et al. 2001, Mol Biol Cell. 12:1791-9). Overexpression of PLK-1 seems to be strongly associated with neoplastic cells including cancers (WO 2004/014899). Overexpression of PLK1 has been documented for various tumor types such as non-small cell lung cancer, squamous cell carcinomas, breast, ovary or papillary carcinomas as well as colorectal cancers (Wolf et al. 1997, Oncogene 14, pages 543-549; Knecht et al. 1999, Cancer Res. 59, pages 2794-2797; Wolf et al. 2000, Pathol Res Pract. 196, pages 753-759; Weichert et al. 2004, Br. J. Cancer 90, pages 815-821; Ito et al. 2004, Br. J. Cancer 90, pages 414-418; Takahashi et al. 2003, Cancer Sci. 94, pages 148-152).
For the treatment of diseases of oncological nature, a large number of chemotherapeutic, immunotherapeutic or immunomodulatory, antiangiogenic or hormonal agents have already been suggested, which can be used as monotherapy (treatment with one agent) or as combination therapy (simultaneous, separate or sequential treatment with more than one agent) and/or which may be combined with radiotherapy or radio-immunotherapy. In this respect, chemotherapeutic agent means a naturally occurring, semi-synthetic or synthetic chemical compound which, alone or via further activation, for example with radiations in the case of radio-immunotherapy, inhibits or kills growing cells, and which can be used or is approved for use in the treatment of diseases of oncological nature, which are commonly also denominated as cancers. In the literature, these agents are generally classified according to their mechanism of action. In this matter, reference can be made, for example, to the classification made in “Cancer Chemotherapeutic Agents”, American Chemical Society, 1995, W. O. Foye Ed.
The efficacy of chemotherapeutic agents can be improved by using combination therapies with other chemotherapeutic, immunotherapeutic, immunomodulatory, antiangiogenic or hormonal compounds. Combination therapies constitute the gold standard in many settings of cancer therapy.
Even if the concept of combining several therapeutic agents or therapies already has been suggested, and although various combination therapies are under investigation and in clinical trials, there is still a need for new and efficient therapeutic compositions for the treatment of cancer diseases, which show advantages over standard therapies.
It is the purpose of the present invention to provide a combination therapy with the PLK Inhibitors of Formula (I) for the treatment of various cancer diseases.